Van der Waals ferromagnetic Josephson junctions

• Published in: Nature communications Vol. 12; no. 1; pp. 6580 - 9
• Main Authors: Ai, Linfeng, Zhang, Enze, Yang, Jinshan, Xie, Xiaoyi, Yang, Yunkun, Jia, Zehao, Zhang, Yuda, Liu, Shanshan, Li, Zihan, Leng, Pengliang, Cao, Xiangyu, Sun, Xingdan, Zhang, Tongyao, Kou, Xufeng, Han, Zheng, Xiu, Faxian, Dong, Shaoming
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.11.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 147/135; 147/3; 639/301/357/1018; 639/766/119/1003; 639/766/119/997; 639/925/927/1064; Coexistence; Coupling; Critical current (superconductivity); Crystals; Ferromagnetism; Heterostructures; Humanities and Social Sciences; Interfaces; Josephson junctions; Laboratories; Magnetic fields; Magnetism; multidisciplinary; Science; Science (multidisciplinary); Superconductivity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-26946-w

Superconductor-ferromagnet interfaces in two-dimensional heterostructures present a unique opportunity to study the interplay between superconductivity and ferromagnetism. The realization of such nanoscale heterostructures in van der Waals (vdW) crystals remains largely unexplored due to the challenge of making atomically-sharp interfaces from their layered structures. Here, we build a vdW ferromagnetic Josephson junction (JJ) by inserting a few-layer ferromagnetic insulator Cr 2 Ge 2 Te 6 into two layers of superconductor NbSe 2 . The critical current and corresponding junction resistance exhibit a hysteretic and oscillatory behavior against in-plane magnetic fields, manifesting itself as a strong Josephson coupling state. Also, we observe a central minimum of critical current in some JJ devices as well as a nontrivial phase shift in SQUID structures, evidencing the coexistence of 0 and π phase in the junction region. Our study paves the way to exploring sensitive probes of weak magnetism and multifunctional building-blocks for phase-related superconducting circuits using vdW heterostructures. The superconductor-ferromagnet interface provides a unique opportunity to study the interplay between superconductivity and ferromagnetism. Here, the authors build a van der Waals ferromagnetic Josephson junction evidencing a strong 0 and π phase Josephson coupling.